scholarly journals The hidden structure dependence of the chemical life of dislocations

2021 ◽  
Vol 7 (16) ◽  
pp. eabf0563
Author(s):  
X. Zhou ◽  
J. R. Mianroodi ◽  
A. Kwiatkowski da Silva ◽  
T. Koenig ◽  
G. B. Thompson ◽  
...  
Keyword(s):  
Mechanical Response ◽  
Material Behavior ◽  
Atomic Scale ◽  
Advanced Materials ◽  
Model Alloy ◽  
Characterization Methods ◽  
Material Chemistry ◽  
Wide Range ◽  
Order Of Magnitude ◽  
Scale Characterization

Dislocations are one-dimensional defects in crystals, enabling their deformation, mechanical response, and transport properties. Less well known is their influence on material chemistry. The severe lattice distortion at these defects drives solute segregation to them, resulting in strong, localized spatial variations in chemistry that determine microstructure and material behavior. Recent advances in atomic-scale characterization methods have made it possible to quantitatively resolve defect types and segregation chemistry. As shown here for a Pt-Au model alloy, we observe a wide range of defect-specific solute (Au) decoration patterns of much greater variety and complexity than expected from the Cottrell cloud picture. The solute decoration of the dislocations can be up to half an order of magnitude higher than expected from classical theory, and the differences are determined by their structure, mutual alignment, and distortion field. This opens up pathways to use dislocations for the compositional and structural nanoscale design of advanced materials.

Atomic-Scale Analysis of Strain Relaxation Mechanisms in Ultra-Thin Metallic Films

2005 ◽  
Vol 880 ◽  
Author(s):  
M. Rauf Gungor ◽  
Dimitrios Maroudas
Keyword(s):  
Plastic Deformation ◽  
Void Growth ◽  
Large Scale ◽  
Mechanical Response ◽  
Strain Relaxation ◽  
Applied Strain ◽  
Atomic Scale ◽  
Elastic Response ◽  
Free Standing ◽  
Wide Range

AbstractA comprehensive computational analysis is presented of the atomistic mechanisms of strain relaxation over a wide range of applied biaxial tensile strain in free-standing Cu thin films. The analysis is based on large-scale isothermal-isostrain MD simulations using slab supercells with cylindrical voids normal to the film plane and extending throughout the film thickness. Our analysis has revealed various regimes in the film's mechanical response as the applied strain level increases. Following an elastic response at low strain (≶ 2%), plastic deformation occurs accompanied by emission of screw dislocations from the void surface and threading dislocations from the film surfaces, in parallel with generation of vacancies due to slip of jogged dislocations. At the lower strain range following the elastic-to-plastic deformation transition (⋚ 6%), void growth is the major strain relaxation mechanism, while at higher levels of applied strain (≥ 8%), a subsequent transition leads to a new plastic deformation regime where void growth plays a negligible role in the film strain relaxation.

Scanning tunneling microscopy of polymers: A status report

1989 ◽  
Vol 47 ◽  
pp. 330-331
Author(s):  
P.E. Russell ◽  
I.H. Musselman
Keyword(s):  
High Resolution ◽  
Scanning Tunneling Microscopy ◽  
Sample Surface ◽  
Atomic Scale ◽  
Constant Current ◽  
Scanning Tunneling ◽  
Status Report ◽  
Tunneling Microscopy ◽  
Research Issues ◽  
Wide Range

Scanning tunneling microscopy (STM) has evolved rapidly in the past few years. Major developments have occurred in instrumentation, theory, and in a wide range of applications. In this paper, an overview of the application of STM and related techniques to polymers will be given, followed by a discussion of current research issues and prospects for future developments. The application of STM to polymers can be conveniently divided into the following subject areas: atomic scale imaging of uncoated polymer structures; topographic imaging and metrology of man-made polymer structures; and modification of polymer structures. Since many polymers are poor electrical conductors and hence unsuitable for use as a tunneling electrode, the related atomic force microscopy (AFM) technique which is capable of imaging both conductors and insulators has also been applied to polymers.The STM is well known for its high resolution capabilities in the x, y and z axes (Å in x andy and sub-Å in z). In addition to high resolution capabilities, the STM technique provides true three dimensional information in the constant current mode. In this mode, the STM tip is held at a fixed tunneling current (and a fixed bias voltage) and hence a fixed height above the sample surface while scanning across the sample surface.

Precipitation at the transformation interface of pearlite in steel

1990 ◽  
Vol 48 (4) ◽  
pp. 912-913
Author(s):  
F. A. Khalid ◽  
D. V. Edmonds
Keyword(s):  
Thin Foil ◽  
Carbon Steels ◽  
Model Alloy ◽  
Low Carbon ◽  
High Carbon ◽  
Growth Interface ◽  
Medium Carbon ◽  
Interphase Precipitation ◽  
Solution Treated ◽  
Wide Range

The austenite/pearlite growth interface in a model alloy steel (Fe-1lMn-0.8C-0.5V nominal wt%) is being studied in an attempt to characterise the morphology and mechanism of VC precipitation at the growth interface. In this alloy pearlite nodules can be grown isothermally in austenite that remains stable at room temperature thus facilitating examination of the transformation interfaces. This study presents preliminary results of thin foil TEM of the precipitation of VC at the austenite/ferrite interface, which reaction, termed interphase precipitation, occurs in a number of low- carbon HSLA and microalloyed medium- and high- carbon steels. Some observations of interphase precipitation in microalloyed low- and medium- carbon commercial steels are also reported for comparison as this reaction can be responsible for a significant increase in strength in a wide range of commercial steels.The experimental alloy was made as 50 g argon arc melts using high purity materials and homogenised. Samples were solution treated at 1300 °C for 1 hr and WQ. Specimens were then solutionised at 1300 °C for 15 min. and isothermally transformed at 620 °C for 10-18hrs. and WQ. Specimens of microalloyed commercial steels were studied in either as-rolled or as- forged conditions. Detailed procedures of thin foil preparation for TEM are given elsewhere.

Atomic scale characterization of GaInN/GaN multiple quantum wells in V-shaped pits

2011 ◽  
Vol 98 (18) ◽  
pp. 181904 ◽  
Author(s):  
Shigetaka Tomiya ◽  
Yuya Kanitani ◽  
Shinji Tanaka ◽  
Tadakatsu Ohkubo ◽  
Kazuhiro Hono
Keyword(s):  
Quantum Wells ◽  
Atomic Scale ◽  
Multiple Quantum Wells ◽  
Multiple Quantum ◽  
Scale Characterization

scholarly journals Combined Macroscopic, Nanoscopic, and Atomic-Scale Characterization of Gold-Ruthenium Bimetallic Catalysts for Octanol Oxidation

2016 ◽  
Vol 33 (7) ◽  
pp. 419-437 ◽  
Author(s):  
Lidia E. Chinchilla ◽  
Carol Olmos ◽  
Mert Kurttepeli ◽  
Sara Bals ◽  
Gustaaf Van Tendeloo ◽  
...  
Keyword(s):  
Bimetallic Catalysts ◽  
Atomic Scale ◽  
Scale Characterization

Experimental Investigation of Ti-6Al-4V with a Biaxial Tensile Test Setup at Elevated Temperature

2014 ◽  
Vol 622-623 ◽  
pp. 273-278 ◽  
Author(s):  
Marion Merklein ◽  
Sebastian Suttner ◽  
Adam Schaub
Keyword(s):  
Elevated Temperature ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Advanced Materials ◽  
Uniaxial Tensile ◽  
Plastic Yielding ◽  
Characterization Methods ◽  
Specific Strength ◽  
Biaxial Tensile ◽  
Stress States

The requirement for products to reduce weight while maintaining strength is a major challenge to the development of new advanced materials. Especially in the field of human medicine or aviation and aeronautics new materials are needed to satisfy increasing demands. Therefore the titanium alloy Ti-6Al-4V with its high specific strength and an outstanding corrosion resistance is used for high and reliable performance in sheet metal forming processes as well as in medical applications. Due to a meaningful and accurate numerical process design and to improve the prediction accuracy of the numerical model, advanced material characterization methods are required. To expand the formability and to skillfully use the advantage of Ti-6Al-4V, forming processes are performed at elevated temperatures. Thus the investigation of plastic yielding at different stress states and at an elevated temperature of 400°C is presented in this paper. For this reason biaxial tensile tests with a cruciform shaped specimen are realized at 400°C in addition to uniaxial tensile tests. Moreover the beginning of plastic yielding is analyzed in the first quadrant of the stress space with regard to complex material modeling.

Atomic Scale Characterization of the Pt/TiO2; Interface

2004 ◽  
Vol 10 (S02) ◽  
pp. 452-453
Author(s):  
Hakim Iddir ◽  
Mark Disko ◽  
Nigel D. Browning ◽  
Serdar Ogut
Keyword(s):  
Atomic Scale ◽  
Scale Characterization

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Simulation of Local Surface Modification in STM by ab initio Quantum Chemistry

1998 ◽  
Vol 05 (02) ◽  
pp. 493-499 ◽  
Author(s):  
V. S. Gurin
Keyword(s):  
Surface Modification ◽  
Ab Initio ◽  
Physical Nature ◽  
Atomic Scale ◽  
Level Shift ◽  
Electrical Field ◽  
High Electrical Field ◽  
Wide Range ◽  
Energy Level Shift ◽  
Ab Initio Approach

Surface modification by means of STM has became a well-known method for the artificial formation of nanometer and atomic scale structures. The physical nature of surface modification can consist in a wide range of phenomena (from mechanical indentation up to specific tip-induced chemistry). The high electrical field at the STM tip is considered to be the main feature of STM modification experiments. The field strength is comparable with intramolecular ones and can influence the chemical bonding in surface structures. The model of STM-stimulated modification is considered using the quantum-chemical ab initio approach for a surface cluster in the high electrical field. The destabilization effect, energy level shift, and bond polarization under the STM tip field occur and can show the atomistic nature of surface transformations in STM.

Uncertainty Quantification in Predicting Behaviour of Rubber-Like Materials in Uni-Axial Loading

2020 ◽  
Author(s):  
Aref Ghaderi ◽  
Vahid Morovati ◽  
Pouyan Nasiri ◽  
Roozbeh Dargazany
Keyword(s):  
Uncertainty Quantification ◽  
Mechanical Response ◽  
Pure Shear ◽  
Constitutive Models ◽  
Material Behavior ◽  
Elastic Behavior ◽  
Deterministic Models ◽  
Data Set ◽  
Material Parameters ◽  
Axial Extension

Abstract Material parameters related to deterministic models can have different values due to variation of experiments outcome. From a mathematical point of view, probabilistic modeling can improve this problem. It means that material parameters of constitutive models can be characterized as random variables with a probability distribution. To this end, we propose a constitutive models of rubber-like materials based on uncertainty quantification (UQ) approach. UQ reduces uncertainties in both computational and real-world applications. Constitutive models in elastomers play a crucial role in both science and industry due to their unique hyper-elastic behavior under different loading conditions (uni-axial extension, biaxial, or pure shear). Here our goal is to model the uncertainty in constitutive models of elastomers, and accordingly, identify sensitive parameters that we highly contribute to model uncertainty and error. Modern UQ models can be implemented to use the physics of the problem compared to black-box machine learning approaches that uses data only. In this research, we propagate uncertainty through the model, characterize sensitivity of material behavior to show the importance of each parameter for uncertainty reduction. To this end, we utilized Bayesian rules to develop a model considering uncertainty in the mechanical response of elastomers. As an important assumption, we believe that our measurements are around the model prediction, but it is contaminated by Gaussian noise. We can make the noise by maximizing the posterior. The uni-axial extension experimental data set is used to calibrate the model and propagate uncertainty in this research.

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